| Date: 09-30-2015 | HC# 091521-529 |
Violi F, Loffredo L, Pignatelli P, et al. Extra virgin olive oil use is associated with improved post-prandial blood glucose and LDL cholesterol in healthy subjects. Nutr Diabetes. July 2015;5:e172. doi: 10.1038/nutd.2015.23.
There is increasing evidence that the Mediterranean diet reduces the risk of cardiovascular events and may help prevent the development of type 2 diabetes. The Mediterranean diet is high in fruits, vegetables, grains, and fish, with moderate consumption of red wine and limited lean meat. Extra virgin oil from olives (Olea europaea, Oleaceae) is also consumed regularly in the Mediterranean diet. The Prevención con Dieta Mediterránea (PREDIMED) study with elderly subjects in Spain found that the Mediterranean diet with extra virgin olive oil (EVOO) helped reduce the risk of developing cardiovascular disease. Oxidative stress is associated with developing type 2 diabetes, and some evidence suggests that EVOO can decrease oxidative stress. The goal of this 2-part, randomized, crossover, blinded study was to measure the effect of EVOO on postprandial glycemic control and lipid profile.
Twenty-five healthy subjects were recruited (13 females and 12 males). The study was conducted between January and March 2013 at Sapienza University in Rome, Italy. The study consisted of 2 phases. During the first phase, all subjects consumed a Mediterranean-style lunch that included pasta, chicken, salad, bread, and an apple (Malus spp., Rosaceae), with or without 10 g EVOO (Lago dei Papi; Viterbo, Italy). The second phase occurred 30 days after the first phase. During the second phase, subjects were divided into 2 groups. Both groups ate the same Mediterranean lunch. In addition, either 10 g of EVOO or corn (Zea mays, Poaceae) oil was added to the lunch. For each phase, blood was drawn before meal consumption and 2 hours after meal consumption. Glucose, insulin, glucagon-like peptide-1 (GLP-1), gastric inhibitory polypeptide (GIP), dipeptidyl peptidase-4 (DPP-4) concentration and activity, low-density lipoprotein cholesterol (LDL-C), oxidized LDL-C (ox-LDL-C), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C) were measured in the blood samples. The data were analyzed with chi-squared tests, Student's t-tests, split-plot analysis of variance, and Spearman rank correlation tests. Blood measures were compared between a meal with no EVOO and one with EVOO in phase 1 and between a meal with EVOO and a meal with corn oil in phase 2.
EVOO added to a meal significantly decreased postprandial blood glucose, DPP-4 concentration and activity, LDL-C, and ox-LDL-C (P<0.001, P<0.001, P<0.001, P=0.014, and P<0.001, respectively) and increased postprandial blood insulin, GLP-1, and GIP (P<0.001, P<0.001, and P<0.05, respectively) when compared to a meal without EVOO. In addition, EVOO added to a meal significantly decreased blood glucose, DPP-4 concentration and activity, LDL-C, and ox-LDL-C (P=0.01, P<0.001, P<0.001, P<0.05, and P<0.001, respectively) and increased insulin and GLP-1 (P<0.001 for both) when compared to a meal with corn oil added. No change was found in TG or HDL-C with EVOO consumption, compared to either corn oil or to no EVOO.
EVOO significantly improved postprandial glucose metabolism by decreasing blood glucose and DPP-4 concentration and activity and increasing insulin and incretin levels (GLP-1 and GIP) when compared to the absence of EVOO or to the presence of corn oil. Incretins, in part, control blood glucose levels by altering insulin activity and secretion. In addition, the decrease in ox-LDL-C with EVOO consumption may indicate a decrease in oxidative stress. Oxidative stress increases DPP-4 activity. DPP-4 is responsible for cleaving incretins and downregulating insulin secretion. These data suggest a possible mechanism by which EVOO increases insulin sensitivity and decreases the risk of developing type 2 diabetes. EVOO also decreased LDL-C. High blood levels of LDL-C are a factor correlated with an increased risk of developing cardiovascular disease. EVOO was much better than corn oil at improving postprandial glucose metabolism, and it would be enlightening to identify the specific compounds within EVOO that are behind this improvement. The authors suggest that oleuropein, found in EVOO, may play an important role in the improvements found in this study. This study may have been limited by the small sample size and the inclusion of only healthy subjects. It would be useful to have the study repeated in patients with metabolic syndrome or type 2 diabetes.
―Cheryl McCutchan, PhD
